The only way to make this better would be to translate the Japanese BIOS then it would be seamless.
128KB or 512KB 16 bit JEDEC type EPROM such as:
27C1024, 27C4096, 27C4002
If you use a 512KB chip (it's what you would use with the multibios anyway) you can put 4 different types of the hacked bioses. :thumbsup: But then you would end needing a switch lol...
The other type of 16bit pinout is not compatible:
27C160, 27C320, 27C322 etc (This JEDEC type is compatible with Megadrive MASK roms and it's the JEDEC type used in the SATURN BOOT ROM)
Last edited by l_oliveira; 03-27-2011 at 11:23 AM.
Try Aisle lord for example. It will lock out on the screen with the SONIC logo. Will not even clean the screen so it crashes very early.
And since the purpose of the hacked BIOS is save people the hassle of modifying the discs, it's intended to boot the original copies therefore it's preferable to use the JPN BIOS which is compatible with your hardware.
All non Japanese games run perfectly on the Japanese bios. I have no idea why non Japanese games have no locks but I suspect it has to do with all of the development kits having their BIOS based on the JPN BIOS. :lol:
this is awesome! I could really use this for my LaserActive
Thanks for this awesome work! :pray:
I actually messed up with AC adaptor years ago on my MCD 1 Jap with bios 1.00.
Results: black screen, no sound, nothing...:crying:
My TV repairman fix it but it only boot on this screen, no sound no music:
I think it come from the eprom bios.
I find someone to burn your region free bios on it, i tell you more when job is done.:-)
(and sorry for my bad English, i'm French.)
That happens when the machine has a HARDWARE fault.
I believe you disassembled it but connected the CD-ROM drive flat cable wrong (inverted, maybe...).
While that won't cause damage, it will not allow the main CPU board detect the CD-ROM drive and you will see that screen without the MEGA-CD logo.
Another possible cause is a poor connection from the MEGA-CD unit to the MEGA DRIVE.
Make sure to inspect it throughy. :thumbsup:
Last edited by l_oliveira; 05-21-2011 at 10:42 PM.
Interesting, I have never seen an EPROM used in a retail Mega-CD before, the socket will certainly make the BIOS replacement a lot easier! (Assuming the socket is not the cause of the problem)
I can just about see a letter/number peeking out from underneath the sticker on the EPROM, so if you carefully peel back the sticker you should be able to see the text printed on the chip which will tell you the original EPROM part number (Dont use too much force though, just slide a piece of paper under the corner of the sticker and gently lift/peel until you can see all the text)
If its not too much trouble please consider taking a picture of the EPROM with the sticker lifted and the empty DIP socket when you remove the EPROM - I only ask as i'm curious to see what EPROM manufacturer/part and type of DIP socket Sega originally used (The socket might even have a manufacturer code on it)
Last edited by link83; 05-22-2011 at 10:35 PM.
Thanks Link for your advice, I posted pictures of my results in my new thread, I don't want to pollute this one.
You can see pictures and references on this page:
Mega-CD Under the Knife, surgeon's opinion needed
@ElBarto: I must ask my friend who will write region free eprom for me.
It should be possible as he like cartmodding. ;-)
Opinions on my new thread are very welcome.
MBM27C1024-15Z (150ns perhaps ?)
The hacked BIOS I use currently was made on top of the dump of this chip.
It's the 911228 bios currently used with emulators, which was dumped by me in 1997 and shared with the internet... ;)
Edit: I just found out there's two versions of the 911228 bios. One is NTSC only and the other is "PAL COMPATIBLE" for southeast Asia. The one I dumped is the southeast Asia version, which is capable of operating properly with both NTSC and PAL displays.
Last edited by l_oliveira; 05-23-2011 at 02:17 PM.
Bios sent to a friend, dump on his way.
I'll try multiregion bios on another working MegaCD Jap next month when i'll receive it.
French LAN & Retrogamming : http://www.asso-sc.com
The JPN and ASIA versions are functionally identical.
What's different is a string on the bios:
ASIA PAL:ERROR!__THIS IS AN NTSC-COMPATIBLE MEGA-CD
_____FOR EXCLUSIVE USE IN JAPAN AND
The older JPN BIOS can only use 64KB Backup RAM cartridges. The PAL BIOS and anything that came after it can use Backup RAM cartridges sized up to 512KB (8192 blocks)ERROR!__THIS IS A PAL-COMPATIBLE MEGA CD
_____FOR EXCLUSIVE USE IN SOUTHEAST ASIA.
And the fact that the JPN bios will GLITCH the title screen graphics when you use it on 50hz.
Last edited by l_oliveira; 06-23-2011 at 12:15 PM.